CN101258667A - Motor for electric power steering system - Google Patents

Abstract

The present invention provides a motor for EPS which can exhibit a desired performance while satisfying severe limitation on physical constitution. In a motor for a rack assist type electric power steering system arranged coaxially around a rack shaft coupled with a steering wheel and supplying a steering assist force to the rack shaft, the motor has a six pole/nine slot structure and the loading ratio (2PF/(ZI/a)) of its magnetic loading (2PF) to electric loading (ZI/a) is set in the range of 100-300. Consequently, a motor for EPS in which physical constitution, output, steering feeling, cost, and the like, are satisfied in good balance can be obtained. Since a numeric value conforming to EPS specification is set for the loading ratio, specification at each part of the motor can be determined in accordance with that value, resulting in optimization of design or reduction in manhour of design.

Description

Electric power motor for steering apparatus

Technical field

The present invention relates to a kind of as driven steering device drive source and the motor that uses particularly relates to a kind of effective technology of inserting the tooth bar booster type electric power steering gear of a rack shaft that is open to traffic at the motor central portion that is applicable to.

Background technology

For the steering force of car assisted grade, a lot of in recent years vehicles have been installed so-called power steering gear.As such power steering gear, from alleviating the angle of engine load and weight reduction etc., the vehicle that electric power steering apparatus (so-called driven steering device) is installed increases to some extent in recent years.This driven steering device (being designated hereinafter simply as EPS) generally is applicable to the transfer of pinion and-rack, according to the allocation position of motor, can be divided into 3 types substantially.Promptly, known have following three types: the tubing string booster type that begins to dispose in steering spindle motor from a motor position side nearer apart from the driver, at the connecting portion of steering spindle and rack shaft the gear booster type of motor is installed, with the tooth bar booster type of the coaxial shape of rack shaft ground installation motor.

EPS in the patent documentation 1 is the device of tooth bar booster type wherein, applies by the motor that is provided with coaxially with rack shaft and turns to auxiliary force.Fig. 3 is the sectional view of formation of the tooth bar booster type EPS of expression patent documentation 1.The EPS51 of Fig. 3 will be produced with the motor 53 of rack shaft 52 coaxial settings turns to auxiliary force, passes to rack shaft 52 by ball screw framework 54.Rack shaft 52 is connected two ends by not shown track rod or steering arm etc. with steered wheel, and is connected in the rack pinion mode with steering spindle 55, goes up action according to driver's steering operation at direction of principal axis (left and right directions among the figure).Motor 53 is in yoke cylindraceous portion 56, and the structure of coaxial insertion magnet 57, armature spindle cylindraceous 58 and rotor core 59 is inserted in armature spindle 58 and is connected with rack shaft 52.

In EPS51, when the direction of operating dish rotates steering spindle 55,, rack shaft 52 realizes steering operation thereby moving to the direction corresponding to this rotation.According to this operation, if the action of not shown steering moment transducer then detects moment according to this and supplies with suitable electric power to motor 53.After motor 53 actions, this rotation is delivered to rack shaft 52 by ball screw framework 54.That is, by ball screw framework 54, the rotation of motor 53 is converted into the axial motion of rack shaft 52, applies to rack shaft 52 and turns to auxiliary force.Turn to auxiliary force and manual steering effort according to this, steered wheel is diverted, thereby alleviates driver's steering wheel operation burden.

Patent documentation 1: the spy opens flat 10-152058 communique

Patent documentation 2: the spy opens the 2004-180449 communique

But the tooth bar booster type EPS of Fig. 3 from the hope demand that is provided with compact in engine room (thin short), many times has strict restriction for its size (physique) (particularly overall dimension).For example, in the EPS that small-sized passenger car is used, in general,, need in the scope below the external diameter 100mm, constitute motor, and establish the optimum specifications of the performance that can satisfy the demands if external diameter surpasses 100mm then lacks product.In addition, the rack shaft of perforation motor inside itself roughly has the external diameter about 20-30mm, and its internal diameter of inserting the armature spindle of wearing also needs about 20-40mm.Therefore, in the motor that tooth bar booster type EPS uses, connect in the structure of central authorities at rack shaft, must be below 100mm with outside diameter control.And, require to obtain desired output, and can realize low friction, low torque fluctuation, low cost with this size.

But such minitype high-performance and EPS motor cheaply when the decision specification, need very careful and loaded down with trivial details adjustment.That is, when the structure of design motor, have the various parameters about magnet and winding etc., it is many that these parameters are in the situation of compromise selection relation.Therefore, for skilled designer, under a lot of situations, setting each specification is very difficult to satisfy above-mentioned each key element, needs to be easy to the design guideline of optimal design.

Summary of the invention

The objective of the invention is to design the EPS motor easily, this EPS can satisfy strict size restrictions with motor, and can give play to desired performance about output, cogging torque and torque ripple etc.

Electric power motor for steering apparatus of the present invention, coaxial be provided in the rack shaft that is connected in steered wheel around, turn to auxiliary force to described rack shaft supply, it is characterized in that the magnetic loading (magnetic mood dress lotus) (2P Φ) of representing described motor and the loading of electric loading (Electricity mood dress lotus) ratio (ZI/a) are 100～300 than (2P Φ/(ZI/a)).

In the present invention, the loading ratio is set at 100～300, can obtains the EPS motor that equilibrium is satisfied size, exported, turns to sense, cost etc.In addition, when motor configuration designed, if according to the specification of above-mentioned numerical value decision motor each several part, the specification that can obtain being suitable for EPS was set.

In above-mentioned electric power motor for steering apparatus, the brushless motor that also can use 6 utmost points, 9 groove structures is as said motor.

In addition, described motor can comprise stator and rotor, described stator comprises housing, be fixed on described housing interior all sides stator core and be wound on winding on the described stator core, described rotor comprises the armature spindle cylindraceous of the rack shaft that is used for inserting logical transfer, is contained in the rotor core cylindraceous on the periphery of described armature spindle, the magnet cover that is installed in the magnet of described rotor core periphery and is contained in the described magnet outside outward outward.At this moment, can be set at above-mentioned external diameter more than the 85mm and below the 100mm.

According to electric power motor for steering apparatus of the present invention, electric power motor for steering apparatus is set around the rack shaft that is connected with steered wheel coaxially, in this motor, the ratio of the magnetic loading of this motor and electric loading is set at 100～300, the best motor that can obtain can balance satisfying size well thus, export, turn to the EPS of sense, cost etc. to use.In addition, about becoming the loading ratio as one of parameter of problem when motor configuration designs, if determine the specification of each one of motor accordingly with above-mentioned numerical value, the specification that then can obtain being suitable for EPS is set, and therefore can realize the optimal design of EPS with motor.In addition, design man-hour,, reduce product cost so can cut down product developing expense because can reduce.

Description of drawings

Fig. 1 shows the sectional view of EPS of the present invention with the formation of motor.

Fig. 2 is the key diagram of the relation of the air-gap amount of comparison magnetic loading type motor and electric loading type motor and effective flux.

Fig. 3 is the sectional view of the EPS structure of expression tooth bar booster type.

Embodiment

Below, with reference to accompanying drawing embodiments of the invention are elaborated.Fig. 1 shows the sectional view of EPS of the present invention with the structure of motor.The motor 1 of Fig. 1 uses as the power source with the EPS of the same tooth bar booster type of Fig. 3, and rack shaft 2 connects the inside of motors 1.But the motor 1 of Fig. 1 is different with the motor 53 of Fig. 3, is brushless motor.The rotation of motor 1 passes to rack shaft 2 by ball screw framework 3, becomes to turn to auxiliary force.

Motor 1 is the device that disposes the inner-rotor type of rotor 21 at outside configuration stator 11, in the inboard.Stator 11 comprises housing 12, be fixed on housing 12 interior all sides stator core 13 and be wound on winding 14 on the stator core 13.Housing 12 is formed by iron etc., and its outside diameter control is within 100mm.Stator core 13 stacked multilayer steel plates and constituting are provided with a plurality of (being 9) tooth herein at interior all lateral processes of stator core 13.In the groove that between tooth, forms (being 9 equally), form the winding 14 that is wound with coil.Winding 14 is connected with battery (not shown) by power supply distribution 15.

Rotor 21 is provided in the inboard of stator 11, and arranged coaxial has armature spindle 22 cylindraceous, rotor core 23, magnet 24 and magnet cover 25.The slotting rack shaft 2 that is connected with in the inboard of armature spindle 22.Rotor core 23 cylindraceous is housed outside on the periphery of armature spindle 22.On the periphery of rotor core 23, be fixed with the magnet 24 of 6 electrode structures.

Magnet 24 uses is small-sized and has the rare earth element magnets such as neodium magnet of high magnetic flux density.So,, can realize the miniaturization of motor, and the inertia of rotor 21 reduces and turns to sense also to be improved by in magnet 24, using rare earth element magnet.The shape of magnet 24 in the form of a ring, N, a plurality of magnetic poles of S alternate configurations in a circumferential direction.In addition, also can use a plurality of magnetic shoes as magnet 24.In the outside of magnet 24, magnet cover 25 is housed outward, even just in case the magnet breakage, can be because of the locked motor 1 of its fragment yet.

Right-hand member side in the figure of housing 12 is equipped with the housing 31 of aluminium die casting system.In housing 31, contain the resolver 33 of the rotation of the bearing 32 of right-hand member side of supporting rotor 21 and detection rotor 21.Resolver 33 is made of resolver stator 34 that is fixed on housing 31 sides and the resolver rotor 35 that is fixed on rotor 21 sides.On resolver stator 34, be wound with coil 36, be provided with magnet exciting coil and magnetic test coil.Be equipped with the resolver rotor 35 that is fixed on the armature spindle 22 in the inboard of resolver stator 34.Resolver rotor 35 constitutes by the laminated metal plate, is formed with protuberance on three directions.

If armature spindle 22 rotates, then resolver rotor 35 also rotates in resolver stator 34.The magnet exciting coil of resolver stator 34 is applied in high-frequency signal, according to protuberance close on and away from, change from the phase place of the signal of magnetic test coil output.By this detection signal and reference signal are compared, thereby detect the turned position of rotor 21.So, according to the turned position of rotor 21, suitably switch the electric current that leads to winding 14, rotation drives rotor 21.

Left end side in the figure of housing 12 is equipped with the housing 41 of aluminium die casting system.In housing 41, ball screw framework 3 is installed.A plurality of balls 44 that ball screw framework 3 comprises nut portions 42, is formed at the spire 43 of the periphery of rack shaft 2, installs between nut portions 42 and spire 43.Rack shaft 2 is under the confined state of the rotation of axle, by nut portions 42 can supporting, and along with the rotation of nut portions 42 moves up at right and left in the mode that left and right directions freely moves back and forth.

Nut portions 42 is fixed on the left part of armature spindle 22, remains free to rotate by the angle bearing 45 that is fixed on the housing 41.With packing ring 46a, 46b be formed between the stage portion 47 of housing 41 inside, angle bearing 45 is fixed with the state that axial action is restricted in the bearing fixing of the peristome that is screwed into housing 41.In addition, the axial action between nut portions 42 and the angle bearing 45 is limited with packing ring 48 and the stage portion 49 that is formed on nut portions 42 peripheries by the bearing fixing that is screwed into nut portions 42 left ends.

In the EPS that possesses such motor 1, at first direction of operating dish, steering spindle are rotated, and rack shaft 2 moves, carries out steering operation to the direction corresponding to this rotation.According to this operation, if not shown steering moment transducer moves, then corresponding to detecting moment, electric power is fed into winding 14 from battery by power supply distribution 15.If electric power supplies to winding 14, then motor 1 moves, armature spindle 22 rotates.If armature spindle 22 rotates, the nut portions 42 that then connects is therewith rotated, and by the effect of ball screw framework 3, rack shaft 2 is transmitted the axial auxiliary force that turns to.In view of the above, promote the mobile of rack shaft 2, assisted diversion power.

But, with in the motor, when decision can meet the demands each specification of performance,, how to distribute magnetic loading and electric loading to become problem in order to suppress motor dimension and to obtain high output at such EPS.At this, the magnetic loading is the summation of motor magnetic flux, and electric loading is the summation of ampere-conductors.The motor that the magnetic loading is big, the ratio of stator core 13 and magnet 24 become big, and in general motor can maximize.The motor relative therewith, that electric loading is big, motor can miniaturizations, but winding temperature is easy to rise.Key element as the distribution that determines magnetic loading and electric loading, have that the influence to characteristic, magnet use amount that inertial change causes change that the influence to cost that causes, influence, the iron quantitative changeization to the twining characteristic that cause because of winding space is little cause to the influence of weight etc., need consider various key elements.

Except these key elements, particularly, with in the motor, also to pay attention to being accompanied by the influence to characteristic part tolerance and rigging error, that cause because of the air-gap quantitative changeization between magnet 24 and the stator tooth at EPS.Fig. 2 is that the air-gap amount of comparison magnetic loading type motor and electric loading type motor and effective flux are (to the magnetic flux of torque; Turn back to the magnetic flux of magnet 24 by tooth from magnet 24) the key diagram of relation.As can be seen from Figure 2, distribute more magnetic loading type motor and distribute more electric loading type motor to compare to electric loading to the magnetic loading, under the identical situation of air-gap amount, the Max. value of useful flux is big (with reference to P, the Q point of Fig. 2).So the magnetic loading distributes bigger motor to belong to high torque (HT) type motor, can improve output.

But, shown in Fig. 2 A, B, in magnetic loading type motor, the variation of the useful flux that changes with respect to air-gap is bigger than electric loading type motor.Therefore, if air-gap measures existing deviation, then useful flux will significantly change, even in build-up tolerance, torque error and fluctuating also will become big, and slot effect (コ ギ Application グ) and torque ripple increase.In the EPS motor, slot effect and torque ripple can cause turning to the deterioration of sense, and be therefore bad.In addition, in magnetic loading type motor, because the magnetic loading is bigger, thus need a large amount of magnet that use high price, thus cause cost to improve, and the use amount of iron also increases, and causes weight to increase.

That is to say that though magnetic loading type motor can be exported torque, its deviation is bigger, on the contrary,, can not obtain big torque though electric loading type motor torque deviation is less.Therefore, for the torque that to need under the situation of strict arrowhead, and suppress torque deviation, improve and turn to sense, consider these merits and demerits, the loading of having analyzed the 6P9S motor that is applicable to EPS distributes.Consequently,, found following phenomenon according to inventor's experiment, that is, the loading shown in the following formula than M in, if the M value is set in 100～300 the scope, then can obtain the EPS motor that equilibrium is satisfied size, exported, turns to sense, cost etc.

Formula 1

$M=\frac{2\mathrm{P\Φ}}{\frac{\mathrm{ZI}}{a}}$

P: number of poles Z: active conductor is counted a: parallel circuits number/2

Φ: the useful flux I of 1 utmost point: specified phase current effective value

At this, it is the conductor number that acts on torque that active conductor is counted Z.The conductor number is that (S * T), for example, in the motor of 10 grooves, 6 circles, the conductor number is 6 * 10=60 to the groove product of counting S and number of windings T.The active conductor number is the part that wherein acts on torque, for example, is 2/3 of conductor number in 3 phase motors.So, with regard to the example of front, Z=60 * 2/3=40.Specified phase current effective value I is the effective value of the motor rated current that flows to certain phase (for example, the U phase in the 3 phase motors) (being to allow lowest high-current value in EPS).What parallel circuits was counted a demonstration is that the circuit of several groups of U, V, W phase is for example arranged in 3 phase motors.

In inventor's experiment, in the motor of 6 utmost points (P=6), 9 grooves, when establishing M=130 (Φ=98069 (the Mx/ utmost point), Z=108 (root), I=84 (Arms), a=1), the external diameter (external diameter of housing 12) of motor 1 can be suppressed at below the 100mm, and when input voltage is 12V, can realize being output as 750W, cogging torque is the following motor of 20mNm.At this moment, because the relation of rack shaft external diameter etc. is difficult to the external diameter of motor is suppressed to not enough 85mm, in motor of the present invention, the motor external diameter is set 90～100mm for, preferably sets for about 85～95mm.In addition, the condition of 100≤M of the present invention≤300 is effective especially for the motor of 6 utmost points, 9 grooves.

In addition, surpass in 300 the magnetic loading type motor in the M value, owing to iron core becomes big, so the weight change is big, and owing to magnet also becomes greatly, so cost increases.Also have, in the motor of 9 grooves, it is big that the deviation of internal diameter becomes, so the deviation of air-gap is bigger, and the fluctuation of torque increases, turns to sense to worsen.On the contrary, in the electric loading type motor of M value less than 100,,, need winding plot ratio, winding cooling provision in consideration insulation, the groove so be easy to heating because coil turn increases.In addition, electric loading type motor is the type of output dependence in electricity supply, and therefore the tendency of the external disturbance of being subject to is arranged, and the influence of the deviation of control is easy to manifest, and the tendency that becomes uppity motor is arranged.

Like this, EPS motor of the present invention, can equilibrium satisfy size, export, turn to sense, cost etc. with obtaining optkmal characteristics as EPS.EPS motor of this small-sized high output finally can fuel saving, and, turn to sense by reducing inertia, can improving based on the rotor miniaturization.In addition, at EPS of the present invention with in the motor, for become when the design motor configuration problem as the loading of one of parameter than M, because set the numerical value that is suitable for the EPS specification in advance, so when structural design, determine the specification of motor each several part to get final product accordingly with it.That is to say,, can be suitable for the design guideline of EPS most according to the present invention.Therefore, and compare in the past, can be easy to obtain small-sized high output, low friction, low torque fluctuation, EPS motor cheaply, can realize optimal design, and can cut down and design man-hour.So, can correspondingly cut down product developing expense, can realize reducing product cost.

In addition, according to inventor's experiment, relatively the magnetic loading section accounts for the magnetic loading footpath (identical with the rotor footpath) of major part herein Account for the electric loading footpath (identical with the stator core footpath) of major part herein with electric loading section

Ratio, as can be known

For good.

The present invention is not limited to the foregoing description, and is self-evident, in the scope that does not break away from its main points, can carry out various changes.

For example, the motor of above-mentioned M=130 only is an example, the self-evident motor that can suitably make other specifications.

Claims (4)

1. electric power motor for steering apparatus, coaxial be provided in the rack shaft that is connected in steered wheel around, supply with to described rack shaft and to turn to auxiliary force, it is characterized in that,

The loading of the magnetic loading (2P Φ) of representing described motor and the ratio of electric loading (ZI/a) is 100～300 than (2P Φ/(ZI/a)).

2. electric power motor for steering apparatus according to claim 1 is characterized in that, described motor is the brushless motor of 6 utmost points, 9 grooves.

3. electric power motor for steering apparatus according to claim 1 is characterized in that described motor comprises stator and rotor,

Described stator comprises housing, be fixed on described housing interior all sides stator core and be wound on winding on the described stator core,

Described rotor comprises the armature spindle cylindraceous of the rack shaft that is used for inserting logical transfer, is contained in the rotor core cylindraceous on the periphery of described armature spindle, the magnet cover that is installed in the magnet of described rotor core periphery and is contained in the described magnet outside outward outward.

4. electric power motor for steering apparatus according to claim 3 is characterized in that, the external diameter of the described housing of described motor is more than the 85mm and below the 100mm.

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